1. Field of the Invention
The present invention relates to a shock absorber, including for use as an additional irreversible shock-absorbing stage together with a component for transferring force.
2. Description of the Related Art
To protect the outer hull of a ship against damage when maneuvering in a port or when anchoring at a wharf, it is known to make use of so-called fenders. Normally, a fender acting as a protective body is thereby positioned between the ship and the wharf such that it serves as a shock absorber on the one hand and, on the other, as a spacer so that the hull is not chafed. Independently devised fenders are usually used for larger ships, these being a component of the wharfage facility. Such fenders designed as components of a wharfage installation can have a certain degree of elasticity so that up to a certain extent they can also act along with the ship's movements when docking or in swells.
When the elastic damping capacity of fenders employed as such is exceeded, however, the risk arises of the ship's hull being damaged since when a ship for example strikes undamped against a wharf, the resultant impact energy acts undampened on the ship's hull. In order to prevent damage to the hull of the ship in this scenario, it is conceivable to provide an irreversibly-designed shock absorber which is activated when the damping capacity of the fender employed is exceeded and then absorbs at least a portion of the resulting impact energy, respectively converts it into the work of deformation and heat.
The damping of impact forces and the effective absorbing of impact energy resulting from an impact is a general problem, particularly with moving objects, when due to the mass of the object, high kinetic energies which are to be absorbed in a defined manner pursuant a predictable sequence of events need to be factored in.
This applies not only to ships such as oil tankers, for which wharfage facilities provide specific impact protection components, but also railborne vehicles. Buffer stops are known from rail technology, for example, which serve to terminate a track or a dead-end track of a railroad line with the intention of preventing a rail vehicle or a railcar from traveling beyond the end of the track. Buffers stops are usually configured so as to absorb as much energy from the moving rail vehicle as possible so that the rail vehicle remains as undamaged as possible. In the process, a buffer stop can be deformed or destroyed.
Shock absorbers can, however, also take the form of bumpers. These relate to structural elements on vehicles which, upon a collision or crash with a hard obstacle, absorb energy and thereby prevent damage to the vehicle or its cargo. Bumpers are particularly used on railborne vehicles (also referred to as “buffers” or “bumper bars”), whereby at least one or two constructional elements affixed to the front end are used which have the purpose of absorbing external compressive forces acting horizontally on the rail vehicle in its longitudinal direction. In line with this principle, rail vehicles can make use of two types of bumpers as shock absorbers, namely the so-called “single buffer” or “central buffer,” in which the shock absorber is mounted in the longitudinal axis of the vehicle such that only one buffer is in each case centrally provided at the front end front beam of the rail vehicle, or the so-called “dual buffer” or “side buffer,” in which two buffers are provided at the front end of the rail vehicle.
It is therefore known from the field of rail vehicle technology, for example, in the case of a multi-member railway vehicle, to equip the individual car bodies with so-called side buffers or UIC buffers when the car bodies are not connected together by a bogie and thus, the distance between the two coupled car bodies can vary during normal vehicle operation. These side buffers thereby serve to absorb and dampen impacts occurring during normal vehicle operation, for example when braking or bringing up to speed.
A telescoped structure can be used for a side buffer utilized on a rail vehicle which includes a buffer housing, a force-transferring member accommodated therein and a damping element, for example in the form of a spring or an elastomer body. With this type of structure, the buffer housing serves as a longitudinal guide and for the supporting of transverse forces while the damping element accommodated in the buffer housing serves in transferring force in the longitudinal direction.
With respect to the overall length as well as the buffer stroke; i.e., the spring travel of the damping element, this is standardized for certain vehicle categories by European regulations (e.g., the UIC 526 and 528 leaflets). The buffer stroke for a standardized UIC buffer, for example, is within a range of from 100 to 110 mm. After reaching maximum buffer stroke, the damping characteristic of the side buffer is exhausted, in consequence of which impact forces which exceed the characteristic operating load of the side buffer are routed to the vehicle undercarriage undampened.
While the impact forces which occur during normal operation of the vehicle, for example between individual car bodies of a multi-member vehicle, are absorbed by the regeneratively-designed damping element integrated in the side buffer, when the operating load of the side buffer is exceeded, however, for instance when the vehicle collides with an obstacle or when the vehicle is abruptly braked, the damping element integrated in the side buffer is usually unable to absorb the total resulting energy. The shock absorbance provided by the side buffer is thus, no longer integrated into the energy-absorbing concept of the vehicle as a whole such that the resulting impact forces are transmitted directly to the vehicle undercarriage. This subjects same to extreme loads with the potential to damage or even destroy same.
With the goal of preventing such damage, it is generally known in rail vehicle technology to design the guiding members of the plunger buffer such that after the maximum buffer stroke has been exhausted; i.e., after the guiding members of the side buffer (buffer sleeve and buffer rod) strike defined arresters, there is an additional contracting possibility by means of controlled deformation.
For example, the WO 2005/11 58 18 A1 printed publication describes a plunger buffer in which after the energy absorption provided by the regeneratively-designed damping element has been exhausted, predetermined break joints break away so as to thus increase the contracting length of the buffer. This increased contracting length allows the plastic deformation of the buffer housing upon overload so that this solution enables a destructive conversion of impact energy into the work of deformation and heat. The resulting deformation of the buffer housing which occurs upon overload thus, provides an additional protection against impacts to the shock absorbance provided by the side buffer.
Even if the side buffer known from this art can protect the vehicle undercarriage up to a certain degree from damage upon severe collisions, it is thereby not possible to adapt the additional shock absorber to specific applications. To do so would require commensurately designing the force-path characteristic for the deformation of the buffer housing so as to enable a predictable, defined absorption of energy. In particular, the known solution is unsuited for many applications since the maximum energy absorption achievable with the deformation of the buffer housing is often too low.
A further disadvantage can be seen in the fact that after the additional shock absorber has been activated, the entire side buffer needs to be replaced since the shock absorber is integrated into the side buffer and because due to the deformation of the buffer housing, the side buffer can no longer be used in normal vehicle operation.
The problem described above not only applies to shock absorbers designed in the form of a bumper; i.e., as a structural element mounted to the front end of a rail vehicle. In fact, a parallel can also be drawn between the disadvantages exemplified above with reference to a side buffer and shock absorbers which are a component of e.g., a buffer stop or a wharfage installation.